Centrifugal equipment



July 25, 1967 P. NYROP 3,332,300

CENTRIFUGAL EQUiPMENT Filed June 10, 1964 5 Sheets-Sheet l INVENTOR. PERNYROP ATTORNEY.

July 25, 1967 I P. NYROP 3,332,300

CENTRIFUGAL EQUIPMENT Filed June 10, 1964 3 Sheets-Sheet 3 INVENTOR. PERNYROP ATTORNEY.

United States Patent 3,332,300 CENTRIFUGAL EQUIPMENT Per Nyrop, Norwalk,Conn., assignor to Don-Oliver Incorporated, Stamford, Conn. Filed June10, 1964, Ser. No. 374,094 9 (Ilairns. (Cl. 74-675) This inventionrelates to drive arrangements in centrifugal equipment of the generaltype in which material being processed is subjected to centripetal forceto separate it into component fractions. More specifically, theinvention pertains to drive arrangements for centrifugal apparatushaving an outer rotary member which confines and exerts centripetalforce upon the process material and a coaxial, inner member rotating ata differential speed which conveys the material axially within the outermember.

Centrifugal equipment of the general type to which the present inventionrelates is shown by United States Patent 3,074,842 to Strong and UnitedStates Patent 2,863,560 to Linke et al. Further, as shown in the Linkeet al. patent, it is known to effect the required differential speedbetween inner and outer rotary members by use of a cycloid drivearrangement in which the rotary members are respectively connected torotate with the cycloid disc or discs and the cycloid cage. A cycloiddrive is a well understood, albeit relatively complex, arrangement whichis described in this specification only to the extent necessary tounderstand the present invention. Further description of the kinematicsand operation of a cycloid drive may be obtained by exemplary referenceto United States Patents 1,694,031 and 1,867,492 to Braren.

It is a characteristic of such cycloid drives that the cycloid disc ordiscs rotate in the same direction but faster than the cycloid cage orhousing. Therefore, in the Linke et al. arrangement the inner rotarymember or material conveyor which is connected to the cycloid cagerotates more slowly than the outer rotary member or cone which isconnected to rotate with the cycloid disc.

It can readily be seen that the cycloid drive arrangement of Linke etal. can be adapted to drive rotary members of the type shown in theStrong patent, and this arrangement is conventional. In such anarrangement, a helically-vaned conveyor is connected to rotate with thecycloid discs and therefore rotates more rapidly than the outer conewhich rotates with the cycloid cage through a connection at thedrive-proximate end of the cone. Although this speed relationship issatisfactory and even preferable in many applications of such equipment,it is occasionally desirable when processing certain materials to havethe conveyor or helix rotating more slowly. This condition isparticularly preferable when maximum liquid removal from a material, forexample a slurry of sugar crystals, is to be accomplished. This reversalof the differential speed relation of course necessitates a reversal ofthe pitch hand of the vanes of the conveyor.

Heretofore, the only cycloid-centrifuge structural arrangement known toaccomplish this desired speed relation, the slower helix, was that shownin the Linke et al. patent. However, this arrangement of rotatingmembers and their respective shafting involves several severedisadvantages. First, because the narrow upper end, that is, thedrive-remote end, of the cone is suspended or connected to the innershaft, feed apertures must be provided through this connection in orderto permit material to enter. The constriction caused by such feedapertures, as compared to the completely open upper end of abottomsupported cone, causes problems in getting adequate and reliablefeed to the centrifugal device. Second, in many applications ofcentrifugal equipment, it is desirable to introduce a wash fluid at someintermediate point in the centrifugal processing of the material. In thetype of centrifugal equipment exemplarily disclosed in thisspecification, a screening centrifuge, it is conventional to introducewash fluid at the upper end of the helix for transmission to one or moreaxially-spaced outlet points in the helix. If the cone weretop-suspended as in the Linke et al. patent, a very complex, expensive,troublesome, sealed arrangement would have to be provided to transmitthe wash fluid through the upper end of the cone to get it to the upperend of the helix. Third, the most severe problem encountered with thetop-suspended cone is the difliculty of preventing cone rocking orrunout, that is, deviation from the central axis of the device. Thisproblem is caused because the lower portions of the cone, which have thegreatest radius and are therefore subjected to the greatest centrifugalforces, are farthest removed from the cone support, and because thesecure attachment of the cone to the upper end of the inner shaft ismore diflicult in view of the reduced bearing area inherently availablethan is the attachment of the cone at its lower end to the outer shaft.

It is also known in the prior art that with other drive arrangements,such as planetary gearing, it is possible to obtain concentric driveshafts wherein the inner shaft rotates more slowly than the outer.However, such drives are far less compact than the cycloid drive and aretherefore disadvantageous as drives for centrifugal equipment. Forexample, comparing the drives necessary to transmit a torque ofmeter-kilograms at the operating speeds involved in one particular sizeof screening centrifuge, a cycloid drive having an axial length of 4inches is required whereas a planetary drive having an axial length ofabout 6 /2 inches is required. Therefore, the cycloid drive is far moreadvantageous for use in the type of centrifugal apparatus to which thepresent invention relates.

Accordingly, it is a primary object of the present invention to overcomethe problems and disadvantages inherent in prior art structures.

To accomplish this object, the present invention provides a uniquecycloid drive arrangement in which the inner of two concentric outputshafts rotates at a slower speed than the outer shaft. This arrangementof course permits the helix to be connected to the slower rotatinginside shaft while a bottom-supported cone can be connected to theoutside shaft. This unique speed relation between the concentric outputshafts of a cycloid drive is accomplished by connecting the inside shaftto the cycloid cage and connecting the outside shaft to rotate with thecycloid discs. To accomplish this connection arrangement in the specificstructure shown in the accompanying drawings, the outside shaft isprovided with an enlarged portion which encompasses the cycloid cage andwhich is connected for rotation with the cycloid discs. A lower axialextension of this enlargement of the out side shaft forms an annularpulley shaft concentric with the conventional eccentric shaft of thecycloid drive. In this manner, the present invention provides anarrangement for a cycloid driven centrifugal apparatus having abottom-supported cone whereby the helix may be driven more slowly thanthe cone.

Accordingly, other objects of the present invention are:

(1) The provision of improved centrifugal equipment in which amaterial-conveying, inner rotary member operates at slower speed than adrive-end-supported, outer rotary member.

(2) The provision of improved centrifuges incorporating a cycloid drivehaving two concentric output shafts wherein the inside shaft rotates ata slower speed.

(3) The provision of cycloid-driven screening centrifuges wherein thehelix of the centrifuge is connected to the cycloid cage and wherein theconical screen support of the centrifuge is connected to rotate with thecycloid discs.

(4) The provision of screening centrifuges, which have bottom-supported,differentially-faster cones, which are more compact than those of theprior art.

(5) The provision of cycloid-driven screening centrifuges havingbottom-supported, differentially-faster cones.

These and other objects of the present invention will become more fullyapparent from the following description and appended claims when read inconjunction with the accompanying drawings in which:

FIGURE 1 is a schematic section of a screening centrifuge in which thecycloid drive arrangement of the present invention has beenincorporated.

FIGURE 2 is a vertical section showing the structure of the rotor and ofthe drive and housing assembly of the centrifuge of FIGURE 1.

FIGURE 3 is a vertical section through the cycloid drive of FIGURE 1.

Referring to the drawings, a screening centrifuge is shown to illustratean exemplary application of the present invention. However, it should beunderstood that the present invention is not limited in its applicationto the particular centrifugal apparatus disclosed.

Referring to FIGURE 1, screening centrifuge It) has an inlet opening 12for feeding process material to a rotor 11 as indicated by arrows 14.The feed material passes to an annular conical space 16 in the rotorbetween a rapidly rotating perforated cone or screen support 18, whichcarries a conical screen (not shown) on its interior surface, and arotating conveyor or helix 20. The rotation of cone 18 urges the processmaterial against the screen. The screen retains one portion of the feedmaterial, for example solids, while another portion of the feedmaterial, for example a liquid, is centrifugally forced through thescreen as indicated by arrows 22. The liquid is collected in one or morechambers 24, 26, and 28 of a centrifuge housing 30. The liquid oreffluent which passes through cone 18 is discharged from the housingchambers 24, 26, and 28 through respective effluent outlets 32, 34, and36 as indicated by arrows 38. The material retained within cone 18 isconveyed axially downwardly by the action of helical vanes 40 on helixwhich rotates in the same direction as cone 18 but at a slightly lowerspeed as fully described hereinafter. The solids are finally dischargedfrom rotor 11 through openings 42 as indicated by arrows 44 and arecollected in a solids chamber 46 of housing to be finally dischargedthrough housing opening 48 as indicated by arrow 50.

As shown generally in FIGURE 1, a drive and housing assembly 58 includesa fixed, double-cone-shaped, support housing 60 having annular bearingassemblies 62 and 64. An annular outer shaft assembly 66 is mounted torotate within bearings 62 and 64 and is connected to the lower, wide endof cone 18. A concentric inner shaft assembly 68 connected to the upperend of helix 20 is mounted by bearing assemblies 70 and 72 to rotatecoaxially within outer shaft assembly 66.

The lower ends of shaft assemblies 66 and 68 are separately connected toa cycloid drive which is completely described hereinafter. The cycloiddrive is powered by a belt pulley 82 which is in turn driven by a beltor belts 84 (FIGURE 2) which extend from a power source such as a motor(not shown) into housing 30 (FIGURE 1) through a suitable belt opening85.

Cycloid drive unit 80 further includes an eccentric shaft 86 which issuitably connected to housing 30. It is known to be desirable in someinstances to incorporate a torque limiting device between the eccentricshaft and the housing and in other instances to rotate the eccentricshaft so as to vary the differential speed relation of the output shaftsof the drive. However, these variations are not shown as they form nopart of the present invention.

As shown in greater detail in. FIGURE 2, rotor 11 includes annular rings91) and 92 suitably secured to the upper open end of cone 18 to formfeed inlet opening 12. Cone 18 is formed by a conical member 94 whichhas a plurality of openings 96 therein for passage of effluent to thefluid chambers surrounding the cone. The cone is secured by screws 98 toa ring 108 containing the solids apertures 42. The ring is in turnsecured by screws 102 to a cone hub 184, and the hub is non-rotatablyconnected to a hollow shaft 186 of outer shaft assembly 66 by anysuitable means such as cap screws (not shown).

Still referring to FIGURE 2, helix 20 includes a lower conical portion110 secured by a key 114 to rotate with a shaft 112 of inner shaftassembly 68. An upper conical portion 116 of the helix is connected tolower portion 110 by cap screws 118 and pins 120. In the particularembodiment illustrated, helix 20 of the screening centrifuge is providedwith two series of passages 122, 124 and 126, 128, 130, 132 to supply awash fluid or fluids from concentric wash fluid feed pipes 134 and 136to the material being processed in the rotor.

Outer shaft assembly 66 further includes a bearing spacer 140 betweenbearings 62 and 64, retaining assembly 146 for hearing 70, and a locknut assembly 148 to retain bearings 62 as well as bearing spacer 140 andbearings 64 in place. Inner shaft assembly 68 is provided with an oilsealing arrangement 142 between cone hub 104 and inner shaft 112 and alock nut assembly 144 to retain bearing 70 on shaft 112. Support housing60 includes a seal assembly 150 to provide a seal between the stationaryhousing and the rotating hub 184. Housing 60 is further provided with aretainer 152 to maintain bearings 64 in position.

Referring to FIGURES 2 and 3, eccentric shaft 86 is suitably mounted 'bya connector (FIGURE 2) to housing 30 of the screening centrifuge. At theupper end of eccentric shaft 86, two eccentric surfaces 162 and 164 areformed on eccentric 166 which is non-rotatably mounted on shaft 86 bykey 168. Eccentric 166 is retained in position on the eccentric shaft bylock nut assembly 178. An oil seal assembly 172 is mounted on theextreme upper end of the eccentric shaft 86 to form a seal between theeccentric shaft and the inner surfaces 174 of the recessed lower end ofinner shaft 112.

Referring now to the pulley driving arrangement for cycloid drive 80,pulley 82 is non-rotatably mounted by a key on an annular shaft 182formed on a lower extension 184 of outer shaft assembly 66. Shaft 182 ismounted for rotation upon eccentric shaft 86 by bearings 184 (FIGURE 2)and 186 (FIGURE 3). Extension 184 of the outer shaft assembly isprovided at its upper end with a retainer 187 for hearing 186, andfurther includes a generally disc-like portion 188 integral with shaft182. Disc-like portion 188 has a plurality of cycloid disc pins 190fixedly mounted therein. Upper and lower cycloid discs 192 and 194 aremounted for rotation about eccentric surfaces 162 and 164, respectively,by roller bearmgs 196. Each cycloid disc has a plurality of circularapertures 198 therethrough, the number of apertures in each disc beingequal to the number of disc pins 190. Plus 190 are each equipped with abushing 200 which has an outside diameter which is smaller than theinside diameter of the apertures 198 by twice the amount of crank throwof the eccentric surfaces. This clearance permits the cycloid discs andthe lower unit 184 of the outer shaft assembly to rotate together aboutdifferent axes at the same speed, that is, one for one.

At the toothed or cycled external peripheries 202 and 264 of cycloiddiscs 192 and 194, respectively, the discs engage a plurality of cagepins 206 mounted in the cycloid cage 288. A retainer 210 to maintain thecycloid discs in position is secured to cycloid cage 288 by cap screws(not shown). Cage 208 is non-rotatably secured to a lower disc-like,integral portion 214 of inner shaft 112 as by cap screws 216.

Lower extension 184 of outer shaft assembly 66 is secured by cap screws220 to a cup-like housing 222 which is formed integrally with outershaft 106. Cup-like portion 222 is further provided with a cylindricalflange 224 spaced from the outer periphery thereof to cooperate with anupstanding cylindrical flange 226 (FIGURE 2) secured on housing 60 toform a seal to keep oil from the drive head from entering the pulleyarea.

In operation, pulley 82 is driven by belt 84 and directly rotatescycloid disc pins 190 as well as the outer shaft assembly 66 which isdirectly connected to cone 18. Revolution of disc pins 190 forcescycloid discs 192 and 194 to rotate about the eccentric axes ofeccentrics 162 and 164. The engagement of the cycles on the externalperiphery of the cycloid discs with cage pins 206 forces ca-ge 208 torotate at an angular velocity determined by the following equation:

Where W is the angular velocity of the eccentric; W2 is the angularvelocity of the cycloid disc; W3 is the angular velocity of the cycloidcage; P is the number of teeth or cycles on the cycloid disc; and S isthe number of teeth or pins on the cycloid cage. With the eccentricstationary (ti/ since P is necessarily less than S, W3 will be less thanW2. Therefore, the cage 208 and inner shaft assembly 63 rotate at alower speed (W3) than does the outer shaft assembly (W2).

Thus, the present invention accomplishes a slower differential rotationof the helix in a screening centrifuge without the necessity and theconsequent disadvantages of suspending the cone from its upper end.

Although the eccentric has been described as being fixed or stationary,it should be noted that without substantial modification of the specificembodiment disclosed, it can be made to rotate so as to vary thedifferential speed relation between the helix and cone according to theabove equation. Therefore, the term speed-controlled eccentric issometimes used below to describe this type of eccentric. As specificallydisclosed herein, the speed may be controlled to be zero.

Although the present invention has been described as applied in ascreening centrifuge, it should be understood that the invention is notso limited. For example, drive units of the present invention canadvantageously be utilized in a so-called centrifugal decanter of a typeknown in the art wherein the outer rotary member is substantiallyimperforate and has within it a helical conveyor.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is illustrative and not restrictive. The scope of theinvention is defined by the appended claims rather than by thedescription preceding them, and all changes which fall within the metesand bounds of the claims, or which are their functional as well asconjointly cooperative equivalents, are therefore intended to beembraced by those claims.

I claim:

1. In a centrifugal processing apparatus having an outer rotary member,a coaxial inner rotary member, and a coaxial, diiferential-speed cycloiddrive unit at the discharge end of said rotary members having aneccentric, a cycloid disc mounted about said eccentric, a cycloid cageengaging the periphery of said disc, first means coaxial with said outerrotary member and connecting said outer rotary member at the dischargeend thereof to said disc to rotate one for one therewith, and secondmeans connecting said cycloid cage to said inner rotary member.

2. A combination as defined in claim 1 together with means for drivinglyrotating said outer rotary member by an external source of power.

3. A combination as defined in claim 1 wherein said respective first andsecond connecting means are outer and inner coaxial shafts,respectively.

4. A cycloid-driven centrifugal apparatus having an outer rotary member,an inner rotary member, and a cycloid drive having an accentric, acycloid disc rotatably mounted about said eccentric, and a cycloid cageen gaging the periphery of said disc, characterized by:

(a) means for driving said outer rotary member;

(b) means connecting said outer rotary member to said cycloid disc torotate one for one therewith;

(c) and means connecting said cycloid cage to said inner rotary memberto rotate said inner rotary member at a differentially slower speed thansaid outer rotary member.

5. In a centrifugal apparatus having an outer rotary member for exertingcentrifugal force upon a material being processed and an inner rotarymember for conveying material axially within the outer member, animproved cycloid drive located at one end of said rotary members andhaving a central axis coaxial with said inner and outer members forrotating them at differential speeds comprising:

(a) an eccentric;

(b) a cycloid disc mounted for rotation about said eccentric;

(c) rotary disc-engaged means connected to said cycloid disc to rotateone for one therewith;

(d) a cycloid cage mounted for rotation about the central axis of saiddrive unit and engaged with the periphery of said eccentrically mountedcycloid disc for differential rotation therewith;

(e) a first shaft means connecting said cycloid cage to said innerrotary member; and

(f) a second shaft means connecting said rotary discengaged means to thedrive proximate end of said outer rotary member.

6. A combination as defined in claim 5 together with means for drivinglyrotating said rotary disc-engaged means.

7. A combination as defined in claim 5 wherein said second shaft 'meansis annular and encompasses said cycloid cage and said first shaft means.

8. In a centrifugal apparatus having an outer rotary member, a coaxialinner rotary member, and a coaxial diiferential speed cycloid drive atthe discharge end of said rotary member, having an eccentric, a cycloiddisc rotatably mounted on said eccentric, and a cycloid cage engagingthe external periphery of said disc characterized by:

(a) a first set of concentric inner and outer shafts extending axiallyfrom one side of said drive;

(b) a second set of inner and outer concentric shafts extending axiallyfrom the other side of said drive;

(c) said inner shaft of said first set being fixedly connected to saidaccentric;

(d) means connecting said outer shaft of said first set with saidcycloid disc to rotate one for one therewith;

(e) said inner shaft of said second set being fixedly connected to saidcycloid cage and being adapted for connection at its drive-remote end toone rotor of the centrifugal apparatus;

(f) and said outer shaft of said second set being fixedly connectedaround said cycloid cage to said outer shaft of said first set and beingadapted for connection at its drive-remote end to the other rotor of thecentrifugal apparatus.

9. For use in a coaxial-dual-rotor centrifugal apparatus,

a cycloid drive having an eccentric, a cycloid disc rotatably mounted onsaid eccentric, and a cycloid cage engaging the external periphery ofsaid disc characterized by:

(a) a first set of concentric inner and outer shafts extending axiallyfrom one side of said drive, said outer shaft being adapted to be drivenby a powered means;

(b) a second set of inner and outer concentric shafts extending axiallyfrom the other side of said drive;

(c) said inner shaft of said first set being fixedly connected to saideccentric;

(d) means connecting said outer shaft of said first set with saidcycloid disc to rotate one for one there- With;

(e) said inner shaft of said second set being fixedly connected to saidcycloid cage and being adapted for connection at its drive-remote end toone rotor of the centrifugal apparatus;

(f) and said outer shaft of said second set being fixedly connectedaround said cycloid cage to said outer shaft of said first set and beingadapted for connection at its drive-remote end to the other rotor of thecentrifugal apparatus.

References Cited UNITED STATES PATENTS Lindenburg 74-805 Cullen 74-801Van Riel 210-374 Boerdijk 74-675 Linke et a1. 210-147 Hils et a1. 74-80510 MARTIN P. SCHWADRON, Primary Examiner.

DAVID J. WILLIAMOWSKY, Examiner.

R. F. HESS, Assistant Examiner.

1. IN A CENTRIFUGAL PROCESSING APPPARATUS HAVING AN OUTER ROTARY MEMBER,A COAXIAL INNER ROTARY MEMBER, AND A COAXIAL, DIFFERENTIAL-SPEED CYCLOIDDRIVE UNIT AT THE DISCHARGE END OF SAID ROTARY MEMBERS HAVING ANECCENTRIC, A CYLOID DISC MOUNTED ABOUT SAID ECCENTRIC, A CYCLOID CAGEENGAGING THE PERIPHERY OF SAID DISC, FIRST MEANS COAXIAL WITH SAID OUTERROTARY MEMBER AND CONNECTING SAID OUTER ROTARY MEMBER AT THE DISCHARGEEND THEREOF TO SAID DISC TO ROTATE ONE FOR ONE THEREWITH, AND SECONDMEANS CONNECTING SAID CYCLOID CAGE TO SAID INNER ROTARY MEMBER.